The composition of the β-2 adrenergic receptor oligomer affects its membrane trafficking after ligand-induced endocytosis
The composition of the β-2 adrenergic receptor oligomer affects its membrane trafficking after ligand-induced endocytosis
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DOI：
10.1124/mol.104.003608
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发表时间：
2005-01-01
影响因子：
3.6
通讯作者：
von Zastrow, M
中科院分区：
文献类型：
--
作者：
Cao, TT;Brelot, A;von Zastrow, M
β2肾上腺素能受体（B2AR）在体内会形成寡聚复合物，这是众所周知的，但这一过程的功能意义尚未完全明了。目前的研究结果确定了人B2AR的寡聚化对稳定转染的人胚胎肾293细胞中激动剂诱导的内吞作用后受体的膜运输的影响。先前已表明，B2AR胞质尾存在的一个序列是内化受体有效再循环所必需的。观察到该序列的突变不仅抑制含有突变的受体的再循环，还抑制共表达的野生型B2AR的再循环。再循环缺陷型突变B2AR的共表达还增强了激动剂诱导的内吞作用后野生型B2AR的蛋白水解降解，这与两种受体以寡聚复合物形式运输到溶酶体是一致的。以相似水平共表达δ阿片受体（DOR）对B2AR的内吞运输产生的影响要小得多，尽管DOR与再循环缺陷型突变B2AR经历相似的膜途径。生化研究证实，在表达匹配的细胞克隆中，B2AR/B2AR - ala同聚复合物比DOR/B2AR异聚体更容易形成，并支持B2AR/B2AR - ala复合物不会被激动剂破坏这一假设。这些结果表明，在配体诱导的内吞作用后，很大一部分B2AR以寡聚复合物形式存在，并且寡聚复合物的组成影响内吞受体在功能不同的再循环和降解膜途径之间的分选。
The beta-2 adrenergic receptor (B2AR) is well known to form oligomeric complexes in vivo, but the functional significance of this process is not fully understood. The present results identify an effect of oligomerization of the human B2AR on the membrane trafficking of receptors after agonist-induced endocytosis in stably transfected human embryonic kidney 293 cells. A sequence present in the cytoplasmic tail of the B2AR has been shown previously to be required for efficient recycling of internalized receptors. Mutation of this sequence was observed to inhibit recycling not only of the receptor containing the mutation but also of the coexpressed wild-type B2AR. Coexpression of recycling-defective mutant B2ARs also enhanced proteolytic degradation of the wild-type B2AR after agonist-induced endocytosis, consistent with trafficking of both receptors to lysosomes in an oligomeric complex. Coexpression of the delta opioid receptor (DOR) at similar levels produced a much smaller effect on endocytic trafficking of the B2AR, even though DOR traverses a similar membrane pathway as recycling-defective mutant B2ARs. Biochemical studies confirmed that B2AR/B2AR-ala homomeric complexes form more readily than DOR/B2AR heteromers in expression-matched cell clones and support the hypothesis that B2AR/B2AR-ala complexes are not disrupted by agonist. These results suggest that a significant fraction of B2ARs exists in oligomeric complexes after ligand-induced endocytosis and that the composition of the oligomeric complex influences the sorting of endocytosed receptors between functionally distinct recycling and degradative membrane pathways.